Hi, I used the manual of a student course for separation into coarse and fine clay. The requirements and calculations are explained in the manual which is available via internet and the link of my former professor: http://soilcrop.tamu.edu/professors/dixon/profile.htm on the homepage you can click on his manual Soil Mineralogy Laboratory Manual Agronomy 626, G. Norman White and J. B. Dixon, 2003. I noticed that the link does not work on my computer - if you have a problem maybe you could just contaxt Dr Dixon - he will be gald to help I think. Regards, Ines

To separate clay size particle from any phyllosilicate type or any other materials using centrifuge, simple centrifugation time is not the key factor but centrifugation force, concentration of the suspension, viscosity of the suspension etc. are also other important key variables. Thus there is no thumb rule and therefore, one has to optimize the time for the individual system one needs to work on.

All centrifuges should have manufacturing literature that is most likely available on the internet.

The applied force is related to the rotational rate, and the distance of the sample

from the axis of rotation. The rotation rate is in RPM ( revolutions per minute ),

The mixture in the bottom of the test tube is the farthest away from the axis of rotation,

and the mixture near the top of the test tube is closest to the axis of rotation.

The applied force is greater near the bottom of the tube.

Hi there, please take a look at Reviews in Mineralogy vol. 28 "Chapter 6. Preparation and Purification of Mineral Dusts by Steve J. Chipera, George D. Guthrie, Jr., and David L. Bish, p. 235 - 250. There should be some interesting tables describing minerals and their particle size, with reference to clay minerals. Hope it helps...